Method for coating surface of moving part of vehicle and moving part of vehicle manufactured by the same

ABSTRACT

A method for coating a surface of a moving part of a vehicle may include a coating preparation process of disposing a screen having a plurality of meshes to be distanced from a surface of the moving part of the vehicle to be coated depending on a predetermined spaced distance; and a coating layer deposition process of forming a coating layer having a pattern having a shape in which a plurality of embossings corresponding to the mesh shape is repeated on the surface of the moving part of the vehicle by a vacuum deposition scheme and forming the coating layer so that the adjacent emboss is connected to each other.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2016-0107411, filed on Aug. 24, 2016, and Korean Patent ApplicationNo. 10-2017-0058246, filed on May 10, 2017, the entire contents of whichis incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method for coating a surface of amoving part of a vehicle and a moving part of a vehicle formed with acoating layer, and more particularly, to a method for coating a surfaceof a moving part of a vehicle and a moving part of a vehiclemanufactured by the same configured for improving frictioncharacteristics by forming a coating layer having continued patterns onthe surface of the moving part of the vehicle.

Description of Related Art

Generally, industrial products, in particular, most parts of a vehicleare parts that are manufactured and then are used for a long time, andthus noise, a fuel loss, or the like occurs when the products are wornor lubrication performance deteriorates, which leads to critical defectssuch as a leak problem of fuel and a reduction in efficiency.

Therefore, various research and developments for securing durability andlow friction characteristics by applying low friction coating tosurfaces of moving parts of a vehicle such as an engine, a camshaft, atappet, and a bronzer have been conducted.

As low friction coating materials that are being put to practical use,there may be diamond like carbon (DLC) using vacuum equipment, tungstencarbide (WC), chrome nitride (CrN), or the like. The so formed coatinglayer has high hardness and excellent low friction characteristics andchemical resistance characteristics.

However, when a demand for a fuel efficiency problem that is consideredto be important in a vehicle industry is increasing, there is alimitation of improving the friction characteristics only by theimprovement in composition, thickness, or the like of the low frictioncoating layer, and therefore it is difficult to satisfy the frictioncharacteristics required for the improvement in fuel efficiency.

Some researchers reported an example of improving additional lowfriction characteristics by a surface pattern or texturing technology.The technology gives shorted patterns having a circle, an oval, or thelike to the low friction coating layer, and therefore a basic materialand a discontinuous pattern are formed and a minute friction aggravationeffect occurs around a pattern to which a heterogeneous material isexposed.

Therefore, the present invention proposes a method for coating a surfaceof a moving part having continued patterns without being shorted bycontrolling a thickness of low friction coating using a screen.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and may not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing amethod for coating a surface of a moving part of a vehicle and a movingpart of a vehicle manufactured by the same configured for improvingfriction characteristics by forming a coating layer having a pluralityof continued patterns on the surface of the moving part of the vehicle.

According to an exemplary embodiment of the present invention, there isprovided a method for coating a surface of a moving part of a vehicle,including: a coating preparation process of disposing a screen having aplurality of meshes to be distanced from a surface of the moving part ofthe vehicle to be coated depending on a predetermined spaced distance;and a coating layer deposition process of forming a coating layer havinga pattern having a shape in which a plurality of embossingscorresponding to the mesh shape is repeated on the surface of the movingpart of the vehicle by a vacuum deposition scheme and forming thecoating layer so that the adjacent emboss is connected to each other.

In the coating layer deposition process, the coating layer may bedeposited by any one of physical vapor deposition (PVD) and chemicalvapor deposition and the coating layer may be made of a materialincluding at least one selected from metals, carbons, nitrides, andcarbides.

The coating layer may have a multi-layer structure in which a pluralityof coating layers having heterogeneous materials are stacked to improvelow friction characteristics.

In the coating preparation process, the screen may be disposed to bedistanced from the surface of the moving part of the vehicle by 0.5 to200 μm.

The method may further include: prior to the coating layer depositionprocess, a buffer layer deposition process of depositing a buffer layeron the surface of the moving part of the vehicle to improve an adhesionof the coating layer.

In the buffer layer deposition process, the buffer layer made of a metalnitride material may be deposited by any one of physical vapordeposition (PVD) and chemical vapor deposition (CVD).

According to another exemplary embodiment of the present invention,there is provided a moving part of a vehicle, in which a surface of themoving part is formed with a coating layer including a plurality ofprotrusions protruding while being distanced from each other at an equalinterval in vertical and horizontal directions thereof and a pluralityof connection parts disposed between the adjacent protrusions to connectbetween the adjacent protrusions and formed to be lower than a height ofthe protrusion.

In the protrusion, the coating thickness rate determined by thefollowing Equation (1) may range from 10 to 95%.Coating thickness rate (%)=B/A×100  (1)

In the above Equation, a may represent the thickness (μm) of theprotrusion of the coating layer and B may represent a thickness (μm) ofa connection part of the coating layer.

More preferably, the coating thickness ratio according to an exemplaryembodiment of the present invention is 25 to 60%.

The protrusion may more protrude by 20 to 40% than a height of theconnection part.

The coating layer may be made of a material including at least oneselected from metals, carbons, nitrides, and carbides and may bedeposited by any one of physical vapor deposition (PVD) and chemicalvapor deposition (CVD).

The moving part of a vehicle may further include: a buffer layerconfigured to be disposed on a bottom surface of the coating layer tominimize a difference in lattice constant between the surface of themoving part of the vehicle and the coating layer.

The buffer layer may be formed at a thickness of 0.1 mm or less.

The buffer layer may include a plurality of buffer protrusions andbuffer connection parts each formed at positions corresponding to theplurality of protrusions and connection parts, and the buffer connectionpart may connect between the adjacent buffer protrusions and is formedto be lower than a height of the buffer protrusion.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating a method for coating asurface having a general pattern according to the related art;

FIG. 2 is a flow chart illustrating a method for coating a surface of amoving part of a vehicle according to an exemplary embodiment of thepresent invention;

FIG. 3 is a diagram schematically illustrating the method for coating asurface of a moving part of a vehicle according to the exemplaryembodiment of the present invention;

FIG. 4 is a photograph illustrating a screen having a plurality ofmeshes used in an exemplary embodiment of the present invention;

FIG. 5 and FIG. 6 are diagrams for explaining a formation of a coatinglayer depending on a spaced distance between the screen and the surfaceof the moving part of the vehicle;

FIG. 7 is a graph showing a coating thickness rate of a coating layerdepending on a spaced distance S;

FIG. 8 is a graph illustrating a relationship between the coatingthickness rate of the coating layer and a friction coefficient;

FIG. 9 is an SEM photograph of the coating layer manufactured accordingto the exemplary embodiment of the present invention;

FIG. 10 is a diagram illustrating a shape of the surface of the coatinglayer according to the exemplary embodiment of the present invention;

FIG. 11 is a diagram illustrating a cross section of the coating layermanufactured according to the exemplary embodiment of the presentinvention; and

FIG. 12 is a graph illustrating measurement results of the frictioncoefficients of the coating layer according to the exemplary embodimentof the present invention and a general non-pattern coating layeraccording to the related art.

It may be understood that the appended drawings are not necessarily toscale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particularly intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

FIG. 1 is a diagram schematically illustrating a method for coating asurface having a general pattern according to the related art.

As illustrated in FIG. 1, in the case of forming a coating layer on asurface of a moving part of a vehicle by a vacuum deposition scheme, thecoating layer is formed by a scheme of first ablating the surface of themoving part of the vehicle by a laser, polishing the surface, removingforeign materials including debris, and performing coating.

However, in the case of forming a pattern by ablating the surface of themoving part of the vehicle by the laser, or the like, the overallcoating process is complicated and the finer the pattern, the longer themachining time, and therefore productivity is reduced, the formation ofthe pattern is non-uniform, or a bump occurs around some of the ablationportion to reduce low friction characteristics.

Therefore, the exemplary embodiment of the present invention forms thecoating layer having a plurality of repetitive emboss shapes to form auniform pattern without the occurrence of the bump by use of a screenhaving a plurality of fine meshes. Here, the coating layer in whichadjacent emboss shapes is connected to each other is formed to improvethe low friction characteristics.

FIG. 2 is a flow chart illustrating a method for coating a surface of amoving part of a vehicle according to an exemplary embodiment of thepresent invention and FIG. 3 is a diagram schematically illustrating themethod for coating a surface of a moving part of a vehicle according tothe exemplary embodiment of the present invention.

As illustrated in FIG. 2 and FIG. 3, the method for coating a surface ofa moving part of a vehicle according to the exemplary embodiment of thepresent invention includes a process of manufacturing the screen, acoating preparation process of disposing the screen to be distanced fromthe surface of the moving part of the vehicle, and a coating layerdeposition process of forming the coating layer on the surface of themoving part of the vehicle.

FIG. 4 is a photograph illustrating a screen having a plurality ofmeshes used in an exemplary embodiment of the present invention.

As illustrated in FIG. 4, a screen 200 according to an exemplaryembodiment of the present invention may be provided to have a shapecorresponding to a pattern of a coating layer on which a plurality ofmeshes 210 are formed.

That is, the screen 200 used in the exemplary embodiment of the presentinvention is repeatedly formed with the plurality of meshescorresponding to each emboss of the coating layer forming apredetermined pattern by repeatedly disposing the plurality of embosses.

At this time, a shape of the mesh 210 may have various shapes includinga quadrangle, a circle, and a diamond but the plurality of meshes 210may preferably have the same shape.

The reason is that the uniform friction characteristics may be formedover the whole surface of the moving part 100 of the vehicle that needsto be formed in the same shape and similar abrasion may be formed overthe whole surface of a deposited coating layer 300, improving a lifespanof products.

The screen 200 used in the exemplary embodiment of the present inventionmay include a metal material having excellent conductivity.

The reason is that the coating layer may be smoothly deposited when thecoating layer is formed by the vacuum deposition scheme.

As described above, when the screen 200 on which the plurality of meshes210 having the same shape are repeatedly formed is prepared, the screen200 is distanced from the surface of the moving part 100 of the vehicledepending on the predetermined spaced distance in the coatingpreparation process.

FIG. 5 and FIG. 6 are diagrams for explaining a formation of a coatinglayer depending on a spaced distance between the screen and the surfaceof the moving part of the vehicle, FIG. 7 is a graph showing a coatingthickness rate of a coating layer depending on a spaced distance, andFIG. 8 is a graph illustrating a relationship between the coatingthickness rate of the coating layer and a friction coefficient.

As illustrated in FIGS. 5 to 8, a spaced distance S according to anexemplary embodiment of the present invention is preferably 0.5 to 5times a thickness of a protrusion 301 of the coating layer 300.

The reason is that to secure a low friction characteristic of a frictioncoefficient of 0.05 or less, the coating layer 300 having apredetermined pattern needs to be formed while the coating thicknessrate determined by the following Equation (1) satisfies 10 to 95%.Coating thickness rate (%)=B/A×100  (1)

At this point, A represents the thickness of the protrusion 301 of thecoating layer 300 and B represents a thickness of a connection part 302.

In other words, the thickness of the protrusion 301 means a thickness ofthe thickest portion of the coating layer, and the thickness of theconnecting part 302 means a thickness of the thinnest part of thecoating layer.

More specifically, the coating thickness rate according to the aboveEquation (1) gradually increases as the spaced distance S increases, andwhen the spaced distance S exceeds 5 times the thickness of theprotrusion 301, the connection part 302 and the protrusion 301 areformed at almost the same height, such that a pattern forming effect isinsignificant and when the spaced distance S is 0.5 times less than thethickness of the protrusion 301, the connection part 302 is not formedand thus the adjacent protrusions 301 are not connected to each otherand the short-circuited coating layer 300 is formed, such that thefriction characteristics may deteriorate.

Accordingly, to form the coating layer 300 formed with a predeterminedpattern at a coating thickness rate of 10 to 95%, it is preferable tospace the screen 200 so that the spaced distance S is 0.5 to 5 times thethickness of the protrusion 301 on the coating layer 300.

More preferably, the coating thickness ratio according to an exemplaryembodiment of the present invention is 25 to 60%. The reason is that tosecure a low friction characteristic of a friction coefficient of 0.035or less.

That is, to form the coating layer 300 having a predetermined patternand formed with the protrusion 301 having a thickness of 0.5 to 40 μm onthe surface of the moving part 100 of the vehicle, the surface of themoving part 100 of the vehicle and the screen 200 are disposed to bedistanced from each other by 0.5 to 200 μm so that the spaced distance Sbetween the surface of the moving part 100 of the vehicle and the screen200 is 0.5 to 5 times the thickness of the protrusion 301 of the coatinglayer 300 to be deposited.

When the coating preparation is completed, the coating layer 300 havinga pattern is deposited on the surface of the moving part 100 of thevehicle by the vacuum deposition scheme during the coating layerdeposition process, and the coating layer is deposited by any a ofphysical vapor deposition (PVD) including sputtering, arc ion plate, orthe like and chemical vapor deposition (CVD).

In the instant case, the coating layer 300 may be deposited with allmaterials including metals, diamond-like carbon (DLC) including silicon(Si), tungsten (W)/chrome (Cr)/titanium (Ti) or pure DLC, carbonsincluding Ta—C, nitrides including chrome (Cr)/molybdenum (Mo)/zirconium(Zr)/aluminum (Al) nitrides, carbides, or the like that may improve thelow friction characteristics.

As described above, the friction characteristics the coating layer 300formed to have a predetermined pattern according to the exemplaryembodiment of the present invention may improve by about 25 to 50%,compared to that of the existing coating layer on which the pattern isnot formed.

The coating layer 300 according to the exemplary embodiment of thepresent invention may have a multi-layer structure in which a pluralityof coating layers having heterogeneous materials are stacked, improvingthe low friction characteristics.

For example, the coating layer 300 may be formed in a multi-layercoating layer in which a first coating layer includes a metal-basedmaterial, a second coating layer includes a nitride-based material, anda third coating layer includes a carbon-based material.

Therefore, the coating layer 300 is formed by stacking the first tothird coating layers made of different materials to have differentfriction characteristics to exhibit different friction characteristicsfor each layer, improving the friction characteristics of the entirecoating layer 300.

Further, since noise vibration absorbing ranges in which noise andvibrations may be absorbed are different depending on a material, amaterial between the respective layers is formed differently to expandthe noise vibration absorbing ranges, simultaneously improving noise,vibration, and harshness (NVH) of the coating layer 300.

FIG. 9 is an SEM photograph of the coating layer manufactured accordingto the exemplary embodiment of the present invention, FIG. 10 is adiagram illustrating a shape of the surface of the coating layeraccording to the exemplary embodiment of the present invention, and FIG.11 is a diagram illustrating a cross section of the coating layermanufactured according to the exemplary embodiment of the presentinvention.

As illustrated in FIGS. 9 and 11, it can be appreciated that the coatinglayer manufactured according to the exemplary embodiment of the presentinvention may be formed with a uniform pattern in which the plurality ofembossings having the same shape, that is, the protrusions 301 arespaced from each other in vertical and horizontal directions thereof.

At this time, the method for coating a surface of a moving part of avehicle according to the exemplary embodiment of the present inventionmay further include a process of depositing a buffer layer 400 toimprove an adhesion between the moving part 100 of the vehicle and thecoating layer 300.

The process of depositing a buffer layer 400 may include a materialsimilar to the coating layer 300 or the moving part 100 of the vehicleand may be formed by the same method as the coating layer 300.

Therefore, a difference in lattice constant between the moving part 100of the vehicle and the coating layer 300 may be minimized to improve theadhesion of the deposited coating layer 300.

In the instant case, the thickness of the buffer layer 400 may bepreferably formed at 0.1 mm or less. The reason is that when thethickness of the buffer layer 400 exceeds 0.1 mm, the buffer layer 400is excessively thick and therefore the manufacturing costs may beincreased.

In an exemplary embodiment of the present invention, the buffer layer400 may include a plurality of buffer protrusions 401 and bufferconnection parts 402 each formed at positions corresponding to theplurality of protrusions 301 and connection parts 302, and the bufferconnection parts 402 connect between adjacent buffer protrusions 401 andis formed to be lower than a height of the buffer protrusions 401.

FIG. 12 is a graph illustrating measurement results of the frictioncoefficients of the coating layer according to the exemplary embodimentof the present invention and a general non-pattern coating layeraccording to the related art depending on a travelling distance.

At this time, the example is an Si-DLC coating layer having a pattern inwhich a quadrangular emboss of 200 μm×200 μm is repeated in the verticaland horizontal directions thereof and the comparative example is theSi-DLC coating layer on which the pattern is not formed, in which afriction coefficient (COF) depending on the travelling distance (m) wasmeasured by rotating the example and the comparative example at a loadof 10N and a linear speed of 500 mm/s under a normal temperature oilcondition to measure.

As illustrated in FIG. 12, the comparative example, that is, thefriction coefficient of the existing non-pattern Si-DLC coating layer onwhich the pattern is not formed is 0.050, while the friction coefficientof the example formed according to the exemplary embodiment of thepresent invention is about 0.030, such that it can be appreciated thatthe friction characteristics are increased by about 40%, compared to thecomparative example.

According to the exemplary embodiments of the present invention, it ispossible to improve the friction characteristics of the moving part ofthe vehicle by forming the coating layer having the predeterminedpattern on the surface of the moving part of the vehicle.

Further, it is possible to improve the productivity by reducing themanufacturing time and the coating costs of the coating layer having thepattern.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “internal”, “outer”, “up”, “down”,“upper”, “lower”, “upwards”, “downwards”, “front”, “rear”, “back”,“inside”, “outside”, “inwardly”, “outwardly”, “internal”, “external”,“internal”, “outer”, “forwards”, and “backwards” are used to describefeatures of the exemplary embodiments with reference to the positions ofsuch features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described toexplain certain principles of the invention and their practicalapplication, to enable others skilled in the art to make and utilizevarious exemplary embodiments of the present invention, as well asvarious alternatives and modifications thereof. It is intended that thescope of the invention be defined by the Claims appended hereto andtheir equivalents.

What is claimed is:
 1. A driving part of a vehicle, wherein a surface ofthe driving part is formed with a coating layer including a plurality ofprotrusions, wherein each of the plurality of protrusions is in a sameshape and distanced from each other at an equal interval in vertical andhorizontal directions to form a uniform pattern on the surface of thedriving, wherein a plurality of connection parts are disposed betweenthe plurality of protrusions being adjacent, wherein the plurality ofconnection parts is formed to be lower than a height of the protrusions,wherein the coating layer has a multi-layer structure formed by stackinga first coating layer, a second coating layer, and a third coatinglayer, each of which is made of a material different from each other,and wherein the first coating layer includes a metal-based material, thesecond coating layer includes a nitride-based material, and the thirdcoating layer includes a carbon-based material.
 2. The driving part ofthe vehicle of claim 1, wherein in the protrusions, a coating thicknessrate determined by the following Equation (1) ranges from 10 to 95%:Coating thickness rate (%)=B/A×100  (1) Wherein A represents a thickness(μm) of the protrusions of the coating layer and B represents athickness (μm) of connection parts of the coating layer.
 3. The drivingpart of the vehicle of claim 2, wherein in the coating thickness rateranges from 25 to 60%.
 4. The driving part of the vehicle of claim 1,wherein the coating layer is made of a material including at least oneselected from metals, carbons, nitrides, and carbides and is depositedby any one of physical vapor deposition (PVD) and chemical vapordeposition (CVD).
 5. The driving part of the vehicle of claim 1, furthercomprising: a buffer layer configured to be disposed on a bottom surfaceof the coating layer.
 6. The driving part of the vehicle of claim 5,wherein the buffer layer is formed at a thickness of 0.1 mm or less. 7.The driving part of the vehicle of claim 5, wherein the buffer layerincludes a plurality of buffer protrusions and buffer connection partseach formed at positions corresponding to the plurality of protrusionsand connection parts, and wherein the buffer connection parts connectbetween adjacent buffer protrusions and is formed to be lower than aheight of the buffer protrusions.